KR20210150697A - Integrated-Optic Biosensor Structure Based on the Evanescent-Field and Two-Mode Power Coupling of Silicon Nitride Rib-Optical Waveguide - Google Patents

Abstract

The present invention relates to an integrated-optic biosensor structure based on a silicon nitride (Si3N4) rib-optical waveguide, which is able to detect the type and concentration of biomaterials by using two-mode optical power engagement and evanescent wave. According to the present invention, the biosensor structure comprises: a lower cladding (200) formed on an upper side of a substrate (100); a core (300) formed on an upper side of the lower cladding (200); and an upper cladding (400) formed on an upper side of the core (300) and having a biomaterial to be diagnosed. On an upper side of the core (300), a rib-optical waveguide (350) for forming an evanescent wave is formed by protruding. The rib-optical waveguide (350) includes: a single-mode rib-optical waveguide (351) into which the light is inputted; a two-mode rib-optical waveguide (352) extended from the single-mode rib-optical waveguide (351) and having a broader width than that of the single-mode rib-optical waveguide (351); and a two-output rib-optical waveguide (353) divided and extended from the two-mode rib-optical waveguide (352) into two branches, and outputting the light. The present invention is able to rapidly and precisely perform a clinical diagnosis on biomaterials with a high degree of sensitivity.

Description

{Integrated-Optic Biosensor Structure Based on the Evanescent-Field and Two-Mode Power Coupling of Silicon Nitride Rib-Optical Waveguide}

The present invention relates to an evanescent wave-based integrated optical biosensor structure, and in particular, silicon nitride (Si ₃ N ₄ ) rib-based optical waveguide-based two-mode optical power coupling and evanescent wave to determine the type and concentration of biomaterials. It relates to an integrated optical biosensor structure capable of sensing.

Clinical diagnostic tests are carried out to determine the diagnosis, treatment, progress and prognosis of a patient's disease. Such clinical diagnosis is made by examining the patient's blood, urine, feces, or a part of body tissue, or by measuring EEG or electrocardiogram. will lose However, most of these conventional clinical diagnostic tests are expensive because their procedures are complicated and require sophisticated equipment operated by specially trained staff. Moreover, these tests often require a time-consuming labeling process for attaching a fluorescent or chemiluminescent marker to a biomaterial to be measured, making the clinical diagnosis process complicated and time-consuming.

Meanwhile, in recent years, a biosensor for examining the properties of a substance by using an enzyme or an antibody of an organism to react with a specific substance is used for clinical diagnosis. However, conventional biosensors used for clinical diagnosis have limitations in that they are complicated to manufacture and have poor precision.

Republic of Korea Patent Publication No. 10-1946456 (Registered on Jan. 31, 2019) Republic of Korea Patent Publication No. 10-1025723 (Registered on March 23, 2011)

The present invention has been proposed to solve the problems of the conventional biosensor for clinical diagnosis, and an object of the present invention is to provide a biosensor structure that does not require a labeling process during clinical diagnostic examination and enables fast and accurate measurement in a narrow device space. there is

The biosensor structure according to the present invention for achieving the above object includes a lower cladding formed on an upper portion of a substrate, a core formed on the upper portion of the lower cladding, and an upper portion formed on the core and on which a biomaterial to be diagnosed is disposed. In the biosensor structure including a cladding, a rib-optical waveguide for forming an evanescent wave is formed to protrude above the core, and the rib-optical waveguide includes a single-mode rib-optical waveguide to which light is input, and the single-mode A two-mode rib-optical waveguide extending to the rib-optical waveguide and having a width relatively wider than that of a single-mode rib-optical waveguide, and the two-mode rib-optical waveguide bifurcated and extended to output light Includes two-output rib-optical waveguides.

Here, the biomaterial is injected into the microfluidic tube inserted into the upper cladding so as to be disposed on the two-mode rib-optical waveguide, and disposed on the two-mode rib-optical waveguide.

Two modes TE00 and TE01 are guided in the rib-optical waveguide, but mode coupling occurs in the two-mode rib-optical waveguide region, and optical power coupling occurs in which optical power periodically moves between the two-modes.

At this time, the mode coupling period occurring in the two-mode rib-optical waveguide region is determined by the effective refractive indices of the two modes to change the two output optical powers of the two-output rib-optical waveguide, and the effective refractive indices of the two-modes are determined. is determined by the refractive index of the biomaterial disposed on top of the two-mode rib-optical waveguide.

Meanwhile, it is preferable that the core and the rib optical waveguide are made of a silicon nitride (Si ₃ N ₄ ) material, and the upper cladding and the lower cladding are made of a silicon dioxide (SiO ₂ ) material.

The single-mode rib-optical waveguide of the rib-optical waveguide has a rib-width of 2 μm, and the two-mode rib-optical waveguide has a rib-width of 4 μm.

In addition, the single-mode rib-optical waveguide and the two-mode rib-optical waveguide have a lip-depth of 5 nm, the two-output rib-optical waveguide has a rib-width of 2 μm, respectively, and the two- The output ports are spaced at a distance of 6 μm.

In addition, it is preferable that the wavelength of the light incident on the rib-optical waveguide is 0.63 μm.

The biosensor structure according to the present invention enables fast and accurate online measurement with high sensitivity when measuring biomolecules by performing a clinical diagnostic test based on the two-mode power combination of silicon nitride lip-optical waveguide and evanescent wave. By integrating a large number of biosensors in a chip, it has the effect of enabling high-level integration and parallel measurement.

1 is a conceptual diagram of an evanescent wave generated in an optical waveguide structure of an integrated optical biosensor according to the present invention;
2 is a structural diagram of a rib optical waveguide of a biosensor rib optical waveguide according to the present invention;
3 is a cross-sectional view AA' of FIG. 2,
4 is a cross-sectional view BB' of FIG. 2,
5 is an example of a computational analysis graph for a single-mode rib-optical waveguide and a two-mode rib-optical waveguide according to the present invention;
6 is a layout structure diagram of a biosensor applied to computational analysis using FIMMPROP software according to the present invention;
7 is an example in which periodic optical power movement occurs between two-modes through periodic two-mode coupling according to the present invention;
8 and 9 are examples in which the output port is changed when the refractive index of the biomaterial according to the present invention is different;
10 and 11 are examples of computational analysis of optical power of two output ports according to a change in refractive index of a biomaterial according to the present invention;
12 is a result of calculating (Pout2-Pout1) in FIG. 10,
13 is a result of calculating (Pout2-Pout1) in FIG. 11,
14 is a sensitivity diagram that is a slope corresponding to the first derivative with respect to FIG. 12;
FIG. 15 shows a sensitivity that is a slope corresponding to the first derivative with respect to FIG. 13 .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows the concept of an evanescent wave generated in an optical waveguide structure of an integrated optical biosensor according to an embodiment of the present invention.

1, the optical waveguide of the biosensor according to the present invention basically includes an upper cladding 400, a core 300, and a lower cladding 200, and most of the light waves incident on the optical waveguide are the core. Proceeding along (300), a very small portion of the light wave appears in the upper cladding 400 and lower cladding 200 regions, and this light wave is referred to as an evanescent wave.

A biomaterial (BM), which is a clinical diagnosis target, is injected into the upper cladding 400 through microfludics 401 , and the evanescent wave integrated optical biosensor includes an evanescent wave and a target molecular material present in the upper cladding 400 . When the biomaterial BM interacts, the effective refractive index of the light wave traveling along the core 300 is affected, and thereby the phase, intensity ( intensity) will eventually change.

Meanwhile, in the present invention, only two modes (TE00 and TE01) are designed to guide the optical waveguide, where TE00 is the basic mode and TE01 is the first higher-order mode. The term "mode" in the present invention means a light wave that travels through the optical waveguide without loss. The mode with the highest effective refractive index and the lowest loss is called the basic mode (TE00), and the next mode is called the first higher-order mode (TE01). . Optical power coupling occurs in which optical power is exchanged between these two modes. At this time, the optical power coupling period is determined by the effective refractive index of each mode, and this effective refractive index is determined by the evanescent wave of each mode. is determined by the refractive index of Therefore, when the biomaterial (BM) is injected into the upper cladding 400 layer through the microfluidic tube 401, the coupling period between the modes is changed, and ultimately, the optical power of one of the two output terminals increases and the other The optical power of one side is decreased. Accordingly, a biosensor capable of diagnosing the type and amount of the biomaterial (BM) injected through the microfluidic tube 401 is implemented when the change in the two output optical powers is used.

2 is a structural diagram of a rib optical waveguide of a biosensor rib optical waveguide according to an embodiment of the present invention.

As shown in FIG. 2 , in the present invention, a rib-shaped optical waveguide in which an evanescent wave appears relatively large in the upper and lower claddings 400 and 200 is implemented in the biosensor. That is, in the biosensor according to the present invention, the rib-optical waveguide 350 protrudes from the upper portion of the core 300 and is integrally formed. The rib-optical waveguide 350 is a single-mode rib-optical waveguide ( 351), a two-mode rib-optical waveguide 352 extending from the single-mode rib-optical waveguide 351, and bifurcated and extended from the two-mode rib-optical waveguide 352 to output light It includes a two-output rib-optical waveguide 353 . In this case, the rib-width of the two-mode rib-optical waveguide 352 is relatively wider than that of the single-mode rib-optical waveguide 351, so that optical power coupling according to mode coupling can be achieved.

On the other hand, in the present invention, in order to realize a high index contrast (HIC) rib-optical waveguide, compatibility with a standard semiconductor process line, high transmittance in the visible region, low loss, low absorption, and _{Silicon nitride (Si 3} N ₄ ) exhibiting high-refractive index-difference characteristics The core 300 and the rib-optical waveguide 350 were formed of a material, and the upper cladding 400 and the lower cladding 200 were formed of a _{silicon dioxide (SiO 2 ) material.} In addition, silicon (Si) is adopted as the lower substrate 100 . Accordingly, the refractive index (ns) of the silicon (Si) substrate 100 is 3.4, the refractive index (n3, n2) of the upper cladding 400 and the lower cladding 200 formed of _{silicon dioxide (SiO 2 ) is 1.46, silicon nitride} The refractive index n1 of the core 300 layer formed of the Ride (Si ₃ N _{4 ) is 2.0.}

A biomaterial (BM) is disposed on the upper cladding 400 to be analyzed by a biosensor, and in the present invention, a microfluidic tube (microfludics) ( 401) was used. That is, in the upper cladding 400 is made of silicon dioxide (SiO ₂₎ material in the invention, two-mode, lip - After removing by etching the silicon dioxide (SiO ₂₎ which is located on top of the optical waveguide 352, a silicon A microfluidic tube 401 having a biomaterial inlet (BM in) and an outlet port (BM out) was disposed at the position where the dioxide (SiO _{2 ) was removed.} Accordingly, when the biomaterial (BM) to be diagnosed is injected into the microfluidic tube 401 and light is incident on the core 300 and the rib-optical waveguide 350, the two-mode lip according to the biomaterial BM -In the optical waveguide 352 , optical power coupling according to mode coupling is made, so that it is output through the two-mode rib-optical waveguide 353 .

On the other hand, in the lip-optical waveguide 350 of the biosensor according to the present invention, the number and types of waveguide modes are the wavelength, core-thickness, lip-width, and lip-depth of the incident light wave. It is entirely determined by the depth.

FIG. 3 is a cross-sectional view of the single-mode rib-optical waveguide region A-A' in FIG. 2, and FIG. 4 is a cross-sectional view of the two-mode rib-optical waveguide region B-B'.

3 and 4, in the embodiment of the present invention, the core-thickness (depth) of the single-mode rib-optical waveguide 351 and the two-mode rib-optical waveguide 352 is 175 nm, The lip-depth is formed to be 5 nm. Also, the single-mode rib-optical waveguide 351 has a rib-width of 2 μm, and the two-mode rib-optical waveguide 352 has a rib-width of 4 μm. In addition, the two-output rib-optical waveguide 353 has a rib-width of 2 μm, respectively, and the two-output ports through which light is output are spaced apart by a distance of 6 μm (see FIG. 6 ). In addition, the total width of the biosensor is 20 μm, and the depth of the lower cladding 200 and the upper cladding 400 is 2 μm. is set

In addition, in the embodiment of the present invention, light having a wavelength of 0.63 μm is incident on the rib-optical waveguide 350, and the light with a wavelength of 0.63 μm is very small in light absorption in the cells constituting the biomaterial to be diagnosed. Because it gives only minimal photo-damage to the cells, it enables the diagnosis of biomaterials without cell loss. The wavelength of such incident light can be appropriately changed according to the specifications of the lip-optical waveguide 350 in the biosensor structure. For example, when a relatively inexpensive silicon photodetector is applied, visible light and near infrared rays of 0.5 μm to 0.9 μm are applied. Biomaterials can be diagnosed using the wavelength region.

In the present invention, a single-mode rib-optical waveguide 351 with a rib-width of 2 μm and a two-mode rib-optical waveguide 352 with a rib-width of 4 μm are used using FIMMWAVE, a commercial software of “Photo Design” company. ), computational analysis was performed for each. 5 shows an example of a computational analysis graph for the single-mode rib-optical waveguide 351 and the two-mode rib-optical waveguide 352, and the computational analysis for 2um and 4um rib-width is single-mode and two-mode. is showing that

Hereinafter, in the biosensor structure having the above structure, mode coupling occurs in the region of the two-mode rib-optical waveguide 352 and optical power transfer between the two-modes will be described.

In an embodiment of the present invention, mode coupling occurs in the region of the two-mode rib-optical waveguide 352 in the biosensor structure according to the present invention using “FIMMPROP” commercial software from “Photon Design”, so that the light between the two modes It was verified that power transfer occurred.

6 shows the layout of the biosensor applied to the computational analysis using the FIMMPROP software, and FIG. 7 is a screen showing the periodic optical power movement between the two-modes through the periodic two-mode combination.

6 and 7, according to the computational analysis using the FIMMPROP software, two modes TE00 and TE01 are guided in the two-mode rib-optical waveguide 352 region, You can see it moving periodically.

The verification screen of FIG. 7 is a result of the two-mode optical waveguide region length L = 3841.46 μm, and the measurement target biomaterial refractive index is set to 1.33. In the region of the two-mode rib-optical waveguide 352, mode coupling occurs between the two modes TE00 and TE01 periodically. In particular, as shown in (a) and (b) of FIG. It can be confirmed through the mode intensity distribution. Also, FIGS. 7C and 7D show that optical power is ultimately output to Pout2 from the two output rib-optical waveguides 350 . As such, in the biosensor structure proposed in the present invention, the period of mode coupling is changed according to the change in the refractive index of the biomaterial with respect to the length of a specific two-mode optical waveguide region, and accordingly, the two output optical powers are sensitively affected. it can be seen that

8 and 9 are screens showing that the output port is changed when the refractive indices of the biomaterial are different.

8 is an example of an optical power output port when the refractive index of a biomaterial is 1.33, and FIG. 9 is an example of an optical power output port when the refractive index of a biomaterial is 1.35. The length of the two-mode rib-optical waveguide 352 region It can be seen that the optical power output from the two output ports is changed according to the refractive index of the biomaterial in a state where is determined.

In addition, when the refractive index of the biomaterial continuously changes in a specific section, the optical power output from the two output ports was verified by applying the commercial software “FIMMPROP”. FIGS. 10 and 11 show two output ports according to the change in the refractive index of the biomaterial An example of computational analysis of the optical power of

10 is a case in which the width W and length L of the two-region rib-optical waveguide 350 are W=4 μm, L=3841.6 μm, and the refractive index range is 1.36 to 1.43, and FIG. 11 shows W=4 μm. , L=26250㎛, and the refractive index range of 1.398 to 1.41 shows the computational analysis.

As shown in FIG. 10 , as the refractive index increases linearly from 1.36 to 1.43, the output power of Pout1 decreases and the output power of Pout2 increases. Also, as shown in FIG. 11 , as the refractive index linearly increases from 1.398 to 1.41, the output power of Pout1 decreases and the output power of Pout2 increases.

In order to evaluate the sensitivity of the biosensor proposed in the present invention, (Pout2-Pout1) can be derived from the two measured optical output powers. 12 is a result of calculating (Pout2-Pout1) in FIG. 10, and FIG. 13 shows a result of calculating (Pout2-Pout1) in FIG. 11. This calculation process is performed using two photodiodes. can be measured using

The sensitivity of such a biosensor is defined as a change in output light according to a change in refractive index. In the present invention, the sensitivity is defined as the change in the difference between the two output lights according to the change in the refractive index, and mathematically corresponds to the slope, which is the first derivative with respect to the graphs of FIGS. 12 and 13 .

14 and 15 show the sensitivity that is the slope corresponding to the first derivative with respect to FIGS. 12 and 13 . As shown in FIG. 14, for the refractive index of the biomaterial in the range of 1.36 to 1.43, the sensitivity is 0.045 to 0.085 (au/RIU), and as shown in FIG. 15, the sensitivity is 0.04-0.1 (au/RIU) for the refractive index range of 1.398 to 1.41 is showing Here, au is an abbreviation for an arbitrary unit, and since the power of the output light is normalized, “au” is used instead of a specific power unit, and RIU is an abbreviation of Refractive Index Unit. It is most desirable to exhibit a characteristic with a uniform sensitivity in a given refractive index range, but the sensitivity level obtained in the present invention is very good, and when measuring the refractive index of a biomaterial, such a sensitivity deviation is sufficient in the subsequent electrical processing process. can be corrected

As described above, in the present invention, the single-mode rib-optical waveguide 351, the two-mode rib-optical waveguide 352, and the two-output rib-optical waveguide 353 are integrally formed on the upper part of the core 300 in the present invention. By providing the rib-optical waveguide 350 structure, the type and amount of the biomaterial can be determined and diagnosed using two output optical powers that change according to the refractive index of the biomaterial.

Meanwhile, in the above-described embodiment, it has been described that the rib-widths of the single-mode rib-optical waveguide 351 and the two-mode rib-optical waveguide 352 are 2 μm and 4 μm, and the incident light has a wavelength of 0.63 μm. However, it is natural that these values can be changed in various ways depending on the type and amount of the biomaterial to be tested.

As such, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made by those of ordinary skill in the technical field to which the present invention pertains within the scope of equivalents of the technical spirit of the present invention and the claims to be described below. Of course, variations can be made.

100: substrate 200: lower cladding
300: core 350: rib-optical waveguide
351: single-mode rib-optical waveguide 352: two-mode rib-optical waveguide
353: two-output rib-optical waveguide 400: upper cladding
401: microfluidic tube BM: biomaterial

Claims (8)

A lower cladding 200 formed on the substrate 100 , a core 300 formed on the lower cladding 200 , and a biomaterial (BM) formed on the core 300 to be a diagnosis target In the biosensor structure including the disposed upper cladding 400,
On the upper portion of the core 300, a rib-optical waveguide 350 for forming an evanescent wave is formed to protrude,
The rib-optical waveguide 350 has a single-mode rib-optical waveguide 351 to which light is input, and is extended to the single-mode rib-optical waveguide 351 and is wider than the single-mode rib-optical waveguide 351 . A two-mode rib-optical waveguide 352 formed relatively wide, and a two-output rib-optical waveguide 353 that is divided into two branches from the two-mode rib-optical waveguide 352 to output light A biosensor structure comprising:
The method of claim 1,
The biomaterial (BM) is
It is injected into the microfluidic tube 401 inserted into the upper cladding 400 so as to be disposed on the two-mode rib-optical waveguide 352 and disposed on the two-mode rib-optical waveguide 352 . Characterized biosensor structure.
3. The method of claim 2,
Two modes TE00 and TE01 are guided in the rib-optical waveguide 350,
A bio material characterized in that mode coupling occurs in the region of the two-mode rib-optical waveguide 352 by the biomaterial (BM) disposed thereon so that optical power coupling in which optical power periodically moves between the two-modes occurs sensor structure.
4. The method of claim 3,
The mode coupling period occurring in the region of the two-mode rib-optical waveguide 352 is determined by the effective refractive indices of the two modes to change the two output optical powers of the two-output rib-optical waveguide 353,
The two-mode effective refractive index is determined by the refractive index of the biomaterial (BM) disposed on the two-mode rib-optical waveguide (352).
5. The method of claim 4,
The core 300 and the rib-optical waveguide 350 are made of a silicon nitride (Si ₃ N ₄ ) material,
The lower cladding 200 and the upper cladding 400 are silicon dioxide (SiO ₂ ) A biosensor structure, characterized in that made of a material.
5. The method of claim 4,
The single-mode rib-optical waveguide 351 of the rib-optical waveguide 350 has a rib-width of 2 μm, and the two-mode rib-optical waveguide 352 has a rib-width of 4 μm. biosensor structure with
7. The method of claim 6,
The single-mode rib-optical waveguide 351 and the two-mode rib-optical waveguide 352 have a rib-depth of 5 nm,
The two-output rib-optical waveguide (353) has a rib-width of 2 μm, respectively, and the two-output ports through which light is output are spaced apart by a distance of 6 μm.
5. The method of claim 4,
The biosensor structure, characterized in that the wavelength of the light incident on the rib-optical waveguide (350) is 0.63㎛.

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